Projection exposure apparatus and exposure method

ABSTRACT

The invention is directed to a projection exposure apparatus for the flat panel display manufacture having an objective array and magnifying objectives (O 1  to O 5 ).

FIELD OF THE INVENTION

[0001] The invention relates to a projection exposure apparatus havingseveral parallelly arranged objectives and a scanning method formicrolithographically exposing large-area structures.

BACKGROUND OF THE INVENTION

[0002] Projection exposure apparatus and scanning methods of the abovekind are disclosed in Japanese patent publications JP 7-057 986, JP7-135 165 and JP 7-218 863.

[0003] In all of these systems, an imaging scale of 1:1 is selected as,for example, in JP 7-135 165, paragraph 15, this imaging scale isprovided for the condition that the mask and exposed plate can beinterconnected during scanning. While this publication discloses lenssystems as projection objectives, the other two Japanese publicationsdisclose catadioptric projection objectives of the Dyson or Offner type.

[0004] Five to seven systems, which operate in parallel, are eachprovided with their own light sources and illuminating optics. Thesystems exhibit polygons as individual image fields (in two offsetlines) which ensure a uniform line by line exposure during scanning.

[0005] No polygonal cropping of the optics is provided in the lenssystems of Japanese patent publication JP 7-135 165. The deflectingmirrors of the catadioptric objectives are shown rectangular in theother two publications but have no reference to the trapezoidal-shapedor hexagonal image fields. In this technology having 1:1 imaging, verylarge format masks are required.

[0006] Systems of this kind are also known in European patentpublication 0,723,173 and U.S. Pat. Nos. 5,614,988; 5,688,624;5,617,211; and, 5,617,181.

[0007] The microlithography for semiconductor manufacture typicallyworks with wafer steppers having objectives with demagnifying imaging ofa factor of 4 or 5 with an image field of approximately 30 mm diameterwith structural widths of 0.3 to 0.5 μm. Scanners increase the ratio ofimage field length to image field width.

[0008] For flat panel displays as in the LCD technology, largeinterconnected structured areas having a more than 10 inch diagonal forstructure widths of typically 3 μm are required. The image fields ofconventional stepper objectives are far too small. Unacceptabledisturbance locations at the transitions between the exposing zones(stitching) would result in accordance with the step method and therepeat method of the wafer steppers.

[0009] European patent publication 0,744,665 discloses an arrangementfor exposing a complete flat panel display (FPD) at once with amagnifying objective having a non-rotational symmetrical element.

SUMMARY OF THE INVENTION

[0010] It is an object of the invention to provide an alternativetechnology for the photolithographic manufacture of large-areastructures. Preferably, masks should be used which correspond to thoseused for microchips.

[0011] The projection exposure apparatus of the invention includes: aplurality of objectives arranged in parallel with each other; and, theobjectives being configured to magnify.

[0012] According to the above, it is a feature of the invention tointroduce magnifying projection objectives into an objective array.

[0013] The structural widths, which are necessary for a flat paneldisplay are relatively large compared to the state of the art for themanufacture of microchips. Accordingly, it is not difficult to providemasks having smaller structural widths than in the product. An areareduction of the mask is achieved thereby in the quadratic ratio whichmakes it substantially easier to manufacture and manipulate the masks.

[0014] The scanning with different speed of mask and wafer has beeninvestigated for the manufacture of microchips with a far greateraccuracy than required for flat panel displays.

[0015] The invention proceeds from the realization that:

[0016] (a) a significant simplification of the entire process isprovided when the masks (reticles) are used from established technologyof microchip manufacture with the conventional size and structuralwidth; and,

[0017] (b) it is known from the demagnifying scanning technology of themicrochip manufacture (even for very tight tolerances) to synchronouslymove reticle and wafer at different speeds.

[0018] According to another feature of the invention, each objective isprovided with its own object mask (reticle).

[0019] Separate reticles for each objective make possible simplercontrollable small reticles which can be controllably adjusted duringoperation.

[0020] According to another feature of the invention, each objective isassigned its own illuminating device and each illuminating device isprovided with a separate light source. The quality of the illuminationand the power of the arrangement (high throughput) is optimized by theparallel arrangement of several illuminating optics and several lightsources.

[0021] According to still another feature of the invention, one orseveral frames of each objective is cut in a polygonal form and one ormore lenses of each objective is (are) configured to have a polygonalform. The image field of each objective has a polygonal form and theabove adaptation of the frames and lenses of the objective to thepolygonal form of the lens permits a very compact configuration of theobjective array and therefore a very stable and effective strip-by-stripscan exposure. The objective can be a pure lens objective and the usethereof utilizes established optical design and permits compact packingof the individual elements of the array such as in more than twoparallelly offset rows.

[0022] The objectives can have an intermediate image and permitarrangements having a one-part reticle.

[0023] The primary area of application of the apparatus and method ofthe invention is for the manufacture of flat panel display structures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will now be described with reference to thedrawings wherein:

[0025]FIG. 1 is a schematic side elevation view of a projection exposureapparatus for the manufacture of a flat panel display with an array ofmagnifying objectives;

[0026]FIG. 2 is a schematic representation of a reticle or reticle arrayhaving strip masks;

[0027]FIG. 3 is a view of the scanning slit image fields and theobjectives as seen from the wafer;

[0028]FIG. 4 is a cross section of an objective which is configured tohave corners;

[0029]FIG. 5 is a side elevation view of a projection exposure apparatushaving an array of magnifying objectives and through masks;

[0030]FIG. 6 is a view of the arrangement of FIG. 5 as seen from awafer; and,

[0031]FIG. 7 is a lens section of a magnifying projection objective.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

[0032] The arrangement of FIG. 1 is a line array and includes threeilluminating systems (B1, B3, B5), a reticle or reticle array R, threeobjectives (O1, O3, O5) and the wafer W. Each of the objectives (O1, O3,O5) magnifies and effects an image reversal. These are normal refractiveobjectives corresponding to the configurations of microlithographicprojection exposure objectives. An example is explained in greaterdetail with respect to FIG. 7.

[0033] A second row (with, for example, two objectives) of objectives(O2, O4) is located behind the objectives (O1, O3, O5) and reticlesections R2 and R4 are assigned to the respective objectives (O2, O4).The second row is not shown for the sake of clarity. Otherwise, theentire arrangement corresponds, like the components, substantially tothe known above-mentioned array exposure apparatus.

[0034] The reticle array is configured in accordance with FIG. 2. Thestructured area of the reticle array is less than the exposed wafer areain correspondence to the imaging scale of the objectives O1 to O5. Thereticle array is subdivided into strips R1 to R5 and each strip isimaged by a corresponding objective O1 to O5.

[0035] The objectives O1 to O5 effect an image reversal. For thisreason, the structures are mirrored on the reticle and the imageextensions are arranged as shown with the letters A, B, C, D.

[0036]FIG. 3 shows a view as seen from the wafer with the tightpackaging of the objectives O1 to O5 in two rows. The packaging isdetermined by the diameter (d) of the objectives. The image fields ofthe objectives (that is, the scanning slits S1 to S5) are so dimensionedthat the entire image field is exposed with a homogeneous intensity whenscanning in the y direction. However, the slits S1 to S5 have atriangular shape at the ends and overlap in this region. The connectionof neighboring regions is smoothed with this known measure. However, thereticle strips R1 to R5 should exhibit corresponding strips twice withidentical structure at the edges.

[0037] The illustrated five-part array structure is only one example andeach line can be placed in the row as desired.

[0038] The reticle R can be in one piece with all structured strips R1to R5 or individual strips can be structured and then precisely adjustedon a carrier and then be assembled to an array. It is even possible toadapt the spacing of the individual strips (software controlled) to therequirements of the image substrate, for example, by distorting theimage substrate after heat treatment. This is only possible for areticle array but not for a large individual reticle. For thispossibility, very slight magnifications of the projection objectives O1to O5 (starting from approximately 1.1 to 1.5) are sufficient.

[0039]FIG. 4 shows how the scanning slits S41 to S45 (otherwise the sameas S1 to S5) can be positioned tighter in the y direction when theobjectives O41 to O45 are cropped by frames and/or by lenses when seenin cross section. This is possible when the object-end lenses aresignificantly greater than the aperture-near lenses and determine theobjective cross section.

[0040] The illumination devices B1 to B5 (FIG. 1) have to fit in eachcase into the measure of the objectives O1 to O5, O41 to O45. This,however, is not easily done because they only illuminate the smallerreticle field.

[0041] A variation, for which a one-part interconnected mask on thereticle R5 is sufficient, is shown in FIG. 5 in schematic side sectionand in FIG. 6 as seen viewed from the wafer. For this purpose, it isnecessary that the reticle side field of the projection objectives O51to O54 has the side offset compared to the image field and that an imagereversal takes place. This is also made possible by the catadioptricobjectives having an intermediate image. Pure mirror objectives are alsopossible.

[0042] Objectives O51 to O55 of this kind can be derived from knowndemagnifying microlithographic projection objectives having anintermediate image wherein object plane and image plane are exchanged.An example is disclosed, for example, in European patent publication0,736,789.

[0043] Reference is now made to FIG. 1 having refractive objectives O1to O5. One embodiment for such an objective is presented with its designdata in Table 1 and shown in the longitudinal lens section of FIG. 7.

[0044] The objective is for a mercury-discharge lamp designed for theline 436 nm and has a four-multiple magnification at an image endnumerical aperture of 0.1 (object end 0.4) and a maximum image height ofy′=26 mm. The structural length is 558 mm and the largest lens diameteris 82 mm. The objective has the typical configuration of refractivemicrolithographic projection exposure objectives, but used formagnification. The RMS image error is less than 0.032 for all imageelevations and the Strehl ratio is greater than 0.96.

[0045] The types of glass listed are optical glasses and arecommercially available from Schott Glas of Mainz, Germany.

[0046] It is understood that the foregoing description is that of thepreferred embodiments of the invention and that various changes andmodifications may be made thereto without departing from the spirit andscope of the invention as defined in the appended claims. TABLE 1Surface Radii Thicknesses Glasses 0 Object 5.760 1 −163.237 5.958 SF1 2148.818 2.164 3 −121.380 4.027 SK4 4 −43.985 42.794 5 −201.332 15.134LAK8 6 −62.781 27.567 7 108.987 15.665 LAK10 8 −452.162 0.286 9 95.42013.971 KF6 10 −218.175 5.001 SF53 11 66.388 10.333 12 63.538 13.994 SF213 62.997 10.640 14 ∞ (Diaphragm) 54.848 15 −49.639 9.957 F5 16 168.25218.229 SK15 17 91.334 0.254 18 223.051 10.996 LAKN12 19 −269.170 80.44720 67.223 14.930 LAKN12 21 874.124 1.009 22 70.226 8.401 BK7 23 106.33013.736 24 −283.133 3.272 BK7 25 34.468 15.000 26 −51.704 10.498 LAF2 27−217.317 61.721 28 141.298 9.427 LAK8 29 −333.793 11.981 30 Image

What is claimed is:
 1. A projection exposure apparatus comprising: aplurality of objectives arranged in parallel with each other; and, saidobjectives being configured to magnify.
 2. The projection exposureapparatus of claim 1, said objectives each being configured to magnifyat a scale greater than 1:1.1.
 3. The projection exposure apparatus ofclaim 2, said objectives each being configured to magnify at a scalegreater than 1:1.5.
 4. The projection exposure apparatus of claim 1,said projection exposure apparatus being a scanning-type projectionexposure apparatus.
 5. The projection exposure apparatus of claim 4,said scanning-type projection exposure apparatus being adapted to scanin a pregiven scan direction; said objectives being arrangedperpendicularly to said scan direction in at least two rows with theobjectives of each row being offset relative to the objectives of thenext adjacent row; and, said objectives having respective individualimage fields seamlessly disposed next to each other or being mutuallyoverlapping.
 6. The projection exposure apparatus of claim 1, each ofsaid individual image fields being so formed that each image pointessentially achieves the same total light dosage even in the overlapregion.
 7. The projection exposure apparatus of claim 1, furthercomprising a plurality of reticles assigned to said objectives,respectively.
 8. The projection exposure apparatus of claim 1, furthercomprising a plurality of illuminating devices assigned to correspondingones of said objectives.
 9. The projection exposure apparatus of claim5, wherein the individual image field of each of said objectives has apolygonal form.
 10. The projection exposure apparatus of claim 9,wherein each of said objectives has at least one frame cut to have apolygonal shape.
 11. The projection exposure apparatus of claim 9,wherein each of said objectives has at least one lens cut to have apolygonal shape.
 12. The projection exposure apparatus of claim 8,wherein each of said illuminating devices has a separate light source.13. The projection exposure apparatus of claim 1, wherein each of saidobjectives is a pure refractive objective.
 14. The projection exposureapparatus of claim 1, wherein each of said objectives is an objectivehaving an intermediate image.
 15. A method for microlithographicallyexposing a large-area structure, the method comprising the steps of:scanning the structure original with a plurality of objectives whicheffectively image a scanning line; and, imaging the structure originalmagnified at a scale greater than 1:1.1.
 16. The method of claim 15,wherein the structure original is magnified at a scale greater than1:1.5.
 17. The method of claim 15, wherein said structure is a flatimage screen structure.